How informal water supply points using private wells worked in an emergency: a quantitative evaluation

The effectiveness of an emergency water supply using private wells has been asserted theoretically but not evaluated in detail. This paper aims to consider the effectiveness and shortcomings of emergency water supply based on local wells and to support policy formulation regarding groundwater usage in the event of a disaster. In Kamisu City, Ibaraki Prefecture, Japan, not only public-operated formal water supply points using water trucks but also informal water supply points using private wells were open to address water outages following the Great East Japan Earthquake of 2011. This study clarified the pattern of appearance and spatial distribution of those points by combining information from local newspapers, Internet archives, and an original questionnaire survey. In addition, the function of informal water supply points was quantitatively evaluated using GIS by comparing cases with and without informal water supply points. Analysis revealed that informal water supply points expanded the size of the serviced population within a 500-m radius of the water supply points by 47%, compared with cases when only formal water supply points were available. However, well water was not necessarily suitable for drinking owing to quality issues. As a policy lesson, the importance of sharing well information is indicated.